Enumerate and explain the two theories regarding the origin of man.?

Question

Enumerate and explain the two theories regarding the origin of man.?

Answer 1

Origin of man... I assume that you are NOT reffering to the dispersal of Homo sapiens but are questioning what hypothesis there are regarding the evolutionary beginnings of hominids. In as such, there are truly NO theories to explain our orgin, just hypothesis, and there are more then two.  One will not become a theory of origin until it stands the test of being empiricaly tested over time and standing up to criticism.  None so far has achieved this enough to be given the status of theory.  

The earliest hypothesis put forth to explain this was the savanna hypothesis, which became discredited when the archaeological record of hominids showed sites previous to the time of savannas being the primary landscape feature in Africa, namely sites that preceded 3 mya (million years ago). Archaeology at this point has even unearthed a few hominid sites that are proposing that early hominids were present even as far back as 6 mya, and if this is the case then the savanna is truly an impossible environment to have allowed our evolution. It was Raymond Dart who first proposed the savanna hypothesis and he did so because he had discovered a significan number of hominids that had lived in South Africa. The archaeological evidence for his site proposed a savanna environment. Being one of the first hominid sites to be found, he was free to conjecture whatever ideas he saw fit from his evidence and hence the birth of the savanna hypothesis. Over the last 25 years, as the savanna hypothesis has been increasingly discredited because of the discovery of sites that date back to earlier times that did not have a savanna environment.

With this fact, contemporary anthropology has more and more began to describing our evolutionionary environment as being that of a mixed hypothesis, which is a primarily arboreal environment with savanna patches between forests. As some Chimpanzee groups live in this "mixed" environment, whereas Bonobos live in a swampy/arboreal environment and display much more incidences of bipedalism, it is my humble opinion that the mixed hypothesis is also flawed in its reasoning, yet that is where anthropology stands on the subject. Other contending hypothesis for the origins of man are:

The ice age hypothesis, which states that Northern Hemisphere ice ages made the African environment drier suddenly, thus forcing the rapic evolution of our species.

The arboreal hypothesis, which states that our constant tree climbing allowed for the adoption of a more upright posture. There are a lot of arboreal monkeys/apes however which are by no means showing the same tendancy so I don't buy this one.

The hypothesis of neotony, which simply states that some undefined rapid environmental change pushed our ancestor towards more generalized neonatal characteristics (baby characteristics) in order to expand our biological toolkit for adaptation.

And my personal favourite, the aquatic hypothesis, which does NOT propose that our hominid ancestors swam in the open ocean as many of it's opponents will have you beleive. In fact their is a lot of geological evidence that shows that the great rift valley flooded around 10-8 million years ago and that this would have resulted in an island remaining in Eretria. The aquatic ape hypothesis postulates that the monkeys that were in this area were forced together onto this Island as the water rose during this period of flooding and as the population became too dense for the remaining terrestrial resources to support this population of monkeys, they began to experiment with new food sources. Over the years one food source that became more and more abundant were the shellfish in the adjacent tidal areas and it was these resources which these monkeys began to exploit (like the crab eating macaques do in South East Asia). As this environment was exploited more and more as a food source, the most successful monkeys were the ones that had advantages (ever so slightly) towards holding their bodies erect as they searched for crabs or oysters (excellent protein source for brain development) in the tidal regions and over many generations (about 1 million years of isolation) bipedalism, a reduced size of our hair, the ability to control our breath, increased fatty tissue, a diving reflex and a whole host of other characteristics came about in these now early hominids. Similiar adaptations took place in a whole bunch of other fully aquatic mammal species like seals, dolphins and whales. The difference with hominids, however, was that the waters receeded after we had only made a partial adaptation towards aquaticism, and as of such they were suddenly left with a new set of characteristics that could be applied within the terrestrial environment where these hominids now found themselves. If these characteristics were not beneficcial then hominids would have gone extinct then and there, but as history has proven, this little, naked hominid stood the test of time and was able to apply his new biological toolkit to adapting to new environments throughout the globe.  

The Aquatic hypothesis is the only opposing hypothesis that has gone to great lengths at giving details concerning our biological adaptations and I find that it successfully competes and is even superior to the ideas currently being put fourth by the mixed hypothesis.  I do not deny that both the ice-age and neotony hypothesis, respectively, could have contributed within the scope of either the mixed or aquatic hypothesis as mechanisms that may have assisted, or hastened our evolution.  It is the aquatic hypothesis  hypothesis, however, that I believe will eventually be given "theory" status once enough empiracle proof is discovered.

So these are the proposed hypothesis regarding the origins of man, and part of the proof that these are indeed hypothesis and not theories is all the bickering that has surrounded their use in anthropology.  I can't wait until more archaeology is done in the danakil hills of Eritria, and hopefully somewhere there were the conditions appropriate towards preservation so that just a few of our earliest hominid relatives can be unearthed thus allowing this hypothesis to spread throughout the archaeological/anthropological community and dethrowning the old-boys-club of archaeology who are ardently holding onto this ridiculous "mixed" hypothesis simply because their life's work has been put towards ideas that depend on it and they don't want to feel like they wasted away their careers. (interestingly enough the old-boys-club which preceeded the current one fought intensely against the "out of Africa" hypothesis being proposed by Raymond Dart and even created the Piltdown hoax to slow the truth from emerging until after Dart's death) Move on and stop creating barriers towards the other hypothesis and the expansion of academic thought in this area. I say this because in the vast majority of undergraduate courses the ONLY perspective which is addressed is the savanna come mixed hypothesis and none of the other hypothesis are even mentioned. Teach these kids how to think! If the theories are wrong then the evidence will prove it and the hypothesis will fade and one true theory will eventually emerge that stands up empiricaly.

These are all the hypothesis of our bipedal roots which were key to our origins and becoming "man".  To elaborate on the use of "theory" in a scientific sense...

see Wikipedia theory:

In science, a theory is a mathematical or logical explanation, or a testable model of the manner of interaction of a set of natural phenomena, capable of predicting future occurrences or observations of the same kind, and capable of being tested through experiment or otherwise falsified through empirical observation. It follows from this that for scientists "theory" and "fact" do not necessarily stand in opposition. For example, it is a fact that an apple dropped on earth has been observed to fall towards the center of the planet, and the theories commonly used to describe and explain this behaviour are Newton's theory of universal gravitation (see also gravitation), and General relativity.

and you can see that in the realm of science that these above hypothesis and creationism do not constitute being "theory" in this regard.  Especially the savana hypothesis which, at this point, has not only not been empiricaly proven but has infact been empiricaly disproven.

The common use of theory, again see wikipedia:

In common usage, people often use the word theory to signify a conjecture, an opinion, or a speculation. In this usage, a theory is not necessarily based on facts; in other words, it is not required to be consistent with true descriptions of reality. True descriptions of reality are more reflectively understood as statements that would be true independently of what people think about them. In this usage, the word is synonymous with hypothesis.

This is why I use the word "hypothesis" to explain these multiple descriptions of our origins, including Creationism.  The problem with creationism is that if you take the bible literaly and compare it to the archaeological record then it also has been disproven empiricaly.  So in the scientific sense creationism and the savana hypothesis have already been scratched off the blackboard when in a discussion of this subject and I only included the savana hypothesis in my discussion for it's historical perspective and as a good example of hypothesis vs theory.

Answer 2

I assume that you refer to evolution and creationism.  

Evolution holds that at some point about 8 million years ago, a separate line of an ape-like species broke off from the "mainline" from which current apes developed.  From this separate line, many species developed and went extinct, while the species developed were more "human-like" than their ancestors, developing social skills and tool skills and cooperative actions to defend themselves against predators.  Homo sapiens is the most recent species considered as man, which developed less than 100,000 years ago and supplanted Neanderthal Man.  

Creationism, on the other hand, holds that man was created in the image of God, and this happened on the sixth day of Creation as related in Genesis I.   Extrapolations from know history consider this time as about 6000 years ago, assuming that the "day" as we know it was the "day" described in Genesis.   Earlier types of man are rules out, although the prologue to Noah's Ark hints at some type of mankind who were totally unacceptable.

Answer 3

The two theories regarding the origin of MODERN humans are the Complete Replacement Theory and Regional Continuity/Multiregional evolution.

The Complete Replacement Theory says Neandertals were a different species; humans evolved out of Africa and replaced all other hominids.

Regional Continuity/Multiregional evolution suggusts there was gene flow between these two groups.

I assume you did not mean creationism, since it is in no way a theory, or even a logical explanation.

Answer 4

There is only one scientific theory and that is evolution by means of natural selection.  All current life on Earth evolved from lower lifeforms and ALL life shares a common ancestor.  It goes much farther than to say we evolved from apes, we evolved from bacteria.  Just so I don't get corrected by those who misunderstand, I didn't say humans evolved from modern apes.

Creation and intelligent design are religious ideas even if some of their proponents are scientists.  Most of those scientists just sell their ideas to a large market so I don't really want to give them legitimacy.